1. Field of the Invention
The present invention relates to internal sizing ring assemblies for use in stuffing tube-like casings, and in particular apparatus and methods for extracting air trapped within a tube-like casing during stuffing operations for producing a substantially air-free shaped product.
2. Description of the Prior Art
Certain food products, such as sausages, cheeses, and deli meats, are produced by stuffing or discharging an emulsion of the desired food product into a flexible, tube-like casing. This stuffing operation is typically performed on a stuffing machine having a pump for forcing the emulsion into the casing. Conventionally, the outlet of the stuffing machine is provided with a stuffing horn, which is a cylindrical tube having an outer surface and a discharge end, through which the emulsion is discharged.
The stuffing horn generally serves two functions. The stuffing horn directs the discharge of the emulsion, and provides a support surface onto which the tube-like casing may be inserted in a sleeve-like manner. The tube-like casing to be stuffed may be either a shirred length of casing, commonly referred to as a shirred stick, or an unshirred, precut casing segment. Likewise, the tube-like casing may be open at both ends, or open only at one end with the other end closed for positioning over the discharge end of the stuffing horn.
Various methods and arrangements are known for performing stuffing operations; specific examples are disclosed in U.S. Pat. Nos. 4,512,059, 4,599,764, 4,646,386, and 4,949,430. One conventional method utilizes an overhorn assembly preloaded with a shirred stick of tube-like casing. The overhorn assembly is adapted to be securely mounted onto the stuffing horn and includes an internal sizing ring fixed on one end, with the tube-like casing arranged to pass over the sizing ring during the discharge of emulsion. The conventional overhorn assembly is configured to open the tube-like casing as it passes over the internal sizing ring to eliminate snags or wrinkles in the tube-like casing. The preloaded shirred stick is either initially open-ended so as to be pulled over the internal sizing ring and sealed closed adjacent the discharge end of the stuffing horn in preparation for stuffing operation, or initially provided with a closed end to be positioned adjacent the discharge end of the stuffing horn. Further, the sizing ring is intended to uniformly feed out or release the casing as the discharge of emulsion forces the closed end of the casing away from the discharge end of the stuffing horn. Once a desired length of casing is stuffed, the casing is sealed shut adjacent the discharge end of the stuffing horn, and severed from the remainder of casing still loaded on the stuffing horn.
In actual stuffing operations, however, the emulsion discharged within the tube-like casing is frequently riddled with air voids. The air voids may be due to sagging or excessive slack in the tube-like casing as it is released from the conventional sizing ring, or the air voids may be created by air initially trapped within the emulsion prior to discharge from the stuffing horn. In either event, portions of the product within the stuffed casing must be down-graded in quality due to the detrimental effects of the air voids, notably destroying the appearance of the product and increasing the risk of bacterial contamination. This down-grading results in the product being sold at a lower price, or requiring reprocessing in an attempt to produce a substantially air-free stuffed casing.
A similar problem occurs in the process of stuffing a tube-like casing for producing a shaped product, such as rectangular loafs or the like. Typically, the method of producing shaped products involves the conventional steps outlined above. However, rather than sealing the casing once a predetermined length of casing is stuffed, the conventional method of producing shaped products further includes pulling an additional length of casing from the stuffing horn. The partially stuffed casing is then sealed shut and pressed inside a container mold to force the emulsion within the casing to conform to the internal cross-section of the container mold.
Inherently air becomes trapped within the casing as the additional length of casing is pulled from the stuffing horn. As such, air voids are naturally prevalent throughout the shaped product, particularly along the end of the casing which was freely pulled from the stuffing horn. Again these air voids result in down-grading of the product, a greater expense to the manufacturer, and a greater health risk to the consumer.